Continuous catalyst regeneration (CCR) naphtha processes are designed to operate at high severity conditions of low pressure, low hydrogen to hydrocarbon ratio and produce high octane reformates for gasoline blending. The desired operating range to sustain steady state white burn regenerator operations for good unit productivity requires that the process generates catalyst coke in a range of 3.0 to 7.0 wt % on the catalyst. Recent environmental regulations have led to a need to operate and produce low octane reformates due to substantial ethanol blending. Over the past years, the concentration of ethanol in the gasoline blend has been 10 vol. %. Recently an increase to 15 vol. % was proposed for cars manufactured after 2007.
In addition and more recently, the price differential between diesel and gasoline has favored more production of diesel and has led to deeper cuts in the naphtha fraction for feed to distillate desulfurization units. The removal of higher boiling naphtha compounds has resulted in low endpoint naphtha feeds for the reformers and these naphtha feeds make much lower spent catalyst coke.
Furthermore, due to the need to minimize expensive gasoline octane give away, refiners are now operating their CCR reformers at low severities that is for the production of lower reformate octanes which lead to catalyst coke production rates that are much lower than desired spent catalyst cokes that are much less than 3 wt. %. Due to concerns with low catalyst flow and sustaining steady state coke burns in regenerators, refiners are opting to shutting down their regenerators for long periods of time in order not to damage equipment such air heaters, disengaging hopper and the regenerator screens. The frequent regenerator outages lead to inadequate catalyst reactivations and, hence, to poor catalyst performance, low unit productivity, uneconomical reformer operations and reliability problems.